Diana Swift
November 18, 2014
Girls who smoke starting from age 13 years may have the greatest risk of experiencing severe chronic pain with their periods, according to a longitudinal population study published onlineNovember 17 in Tobacco Control.
Previous studies have suggested that smoking could increase the risk for severe menstrual pain, which affects 2% to 29% of women, but the data have been inconclusive. Now that connection appears strengthened by Australian research, led by epidemiologist Hong Ju, PhD, from the University of Queensland’s School of Population Health, Herston, Australia.
Tracking dysmenorrhea patterns in 9068 participants from 2000 onward in the Australian Longitudinal Study on Women’s Health, the researchers found that early initiation of smoking was especially associated with developing chronic dysmenorrhea. That finding underscores the need to target antismoking programs to young adolescents, the authors note. “In addition, smoking cessation should be strongly encouraged as women may recover from dysmenorrhea after quitting smoking,” they write.
At baseline, in 1996, the entire cohort of 14,427 women in 1973–1978 Australian Longitudinal Study on Women’s Health cohort was representative of the Australian population and ranged in age from 18 to 23 years. They were sent survey questionnaires every 3 to 4 years, most recently in 2012.
In the current study, the researchers analyzed data from the subset of women who reported having dysmenorrhea in at least three of the surveys, starting with the survey from 2000. At that time, 24.5% of the participants reported dysmenorrhea and 26.4% were current smokers. In addition, 7.3% reported having started smoking by age 13 years, 14% by age 14 to 15 years, and 8.2% before menarche.
The researchers used the repeated survey data to follow the women’s longitudinal reports of dysmenorrhea. They categorized women based on smoking status (current, former, or never smoking status), the amount smoked daily, age at smoking initiation, and age at initiation relative to age at menarche.
Overall, about 60% of the women reported experiencing symptoms at some time during the monitoring period. The researchers divided the women into four groups by pain type and duration. The normative group (42%) had no or few symptoms, whereas the late-onset group (11%) had increasing prevalence of period pain, going from 15% to nearly 70%. The recovering group (33%) had a decreasing prevalence of period pain, going from 40% at ages 22 to 27 years to 10% by ages 34 to 39 years. In addition, 14% of the women fell into the chronic group, reporting a high prevalence of period pain of between 70% and 80% throughout the monitoring period.
The prevalence of period pain was slightly higher in current smokers (29%) than in nonsmokers (23%), and smokers were more likely to report severe pain lasting more than 2 days.
Compared with never-smokers, ex-smokers had a 33% greater risk of chronic symptoms (odds ratio, 1.33; 95% confidence interval, 1.05 – 1.68), and current smokers had a 41% increased risk (odds ratio, 1.41; 95% confidence interval, 1.17 – 1.70). The researchers adjusted the analyses for socioeconomic status, lifestyle and reproductive factors.
Interestingly, in those who started to smoke before or by age 13 years, the investigators saw a 59% higher risk (odds ratio, 1.59; 95% confidence interval, 1.18 – 1.90) after adjusting for other factors.
These findings are compatible with previous studies of smoking and dysmenorrhea risk and severity. Women who start smoking early may have a longer overall duration of smoking, which is associated with increased dysmenorrhea risk. Women who quit smoking after baseline were less likely to be in the chronic and late-onset groups.
There was also a trend to increased odds with age at initiation and age at menarche (P = .002).
Although the precise biological mechanisms of smoking and dysmenorrhea are not known, smoking has been shown to cause vasoconstriction, potentially resulting in pain.
It has also been suggested that smoking may directly affect the endocrine control of menstruation, as it can be related to other problems such as prolonged periods, which are also associated with dysmenorrhea. Smoking may have a particular effect on the hormonal milieu in the sensitive time before onset of regular menstrual cycles in young girls.
Another explanation offered is that the central nervous system may play a role in menstrual pain intensity, and there may be psychological differences in the ways smokers and nonsmokers experience pain. The authors, however, say the facts do not support this theory, as it has been observed that the risk for dysmenorrhea in exsmokers is similar to that that of never-smokers.
The study also found an enhanced risk in women who were unemployed, had early menarche, were obese, or spoke a European language at home.
This research was funded by the Australian Longitudinal Study on Women’s Health, supported by the Australian Government Department of Health. The authors have disclosed no relevant financial relationships.
Tobacco Control. Published online November 17, 2014. Abstract